Retailing businesses and banking institutions are currently suffering substantial financial losses due to unauthorized use of credit cards in the conduct of business at the consumer level. The problem of detecting counterfeit credit cards and unauthorized users of valid cards prior to completion of credit-card transactions has not been effectively solved to date. Banking institutions which are equipped with card-operated banking equipment are generally able to detect an attempted unauthorized use of a credit card because such banking equipment is conveniently connected to the institution's central processor and computer files for "on-line" operation of the equipment at each step in a credit-card transaction. However, the great majority of credit-card transactions by retailers around the world is usually completed in amounts under set credit limits without the convenience of "on-line" computer checking of each step in the transaction. Instead, simple "off-line" credit-card checking techniques are used which are based upon a comparison of the card number against a compiled listing of numbers of unauthorized cards and a visual check of a user's signature against a sample signature. Such lists of numbers of unauthorized cards are largely ineffective in reducing credit losses because of the delay in compiling and distributing the lists, and because such lists do not identify valid cards that have been reproduced or counterfeit cards that bear fictitious numbers.
Even inherently more secure transactions which are controlled by "on-line" interactive computer processing are subject to security violations resulting from insufficiently secured procedures used in issuing cards initially. Unscrupulous personnel within a card-issuing institution may compromise the security of an "on-line" card-operated, computer-controlled system, for example, by causing issuance of a card with an account or identification number that was previously assigned.